Scalable Routing Protocols for Mobile Ad Hoc Networks Xiaoyan Hong, Kaixin Xu, and Mario Gerla at UCLA

Dealing with mobility and scalability Main problems: 1.moving nodes 2.large number of nodes 3.limited communication resources

Main topics: 1.Flat routing protocols 2.Hierarchical routing protocols 3.Geographic position assisted routing protocols

Flat routing protocols Two basic categories: 1.Proactive (table-driven) 2.Reactive (on-demand)

Proactive protocols 1.FSR (Fisheye State Routing) 2.FSLS* (Fuzzy Sighted Link State) 3.OLSR (Optimized Link State Routing) 4.TBRPF (Topology Broadcast Based on Reverse Path Forwarding)

FSR A simple, efficient LS type routing protocol FSR exchanges the entire link state information only with neighbors Link state exchange is periodical Periodical broadcasts of LS info are conducted in different frequencies depending on the hop distances

OLSR OLSR uses multipoint relays to reduce superfluous broadcast packet retransmission and also the size of the LS packets OLSR thus leads to efficient flooding of control messages in the network

OLSR (cont’d) Only the multipoint relays nodes (MPRs) need to forward LS updates OLSR is particularly suited for dense networks In sparse networks, every neighbor becomes a multipoint relay, then OLSR reduces to pure LS protocol

TBRPF Consists of two modules: the neighbor discovery module (TND) and the routing module TND send differential HELLO messages that reports only the changes of neighbors. The routing module operates based on partial topology information

TBRPF (cont’d) TBRPF only propagates LS updates in the reverse direction on the spanning tree formed by the minimum-hop paths. Only the links that will result in changes to the source tree are included in the updates

On-demand Routing Protocols 1.AODV (Ad Hoc On-demand Distance Vector routing) 2.DSR (Dynamic Source Routing)

AODV Using backward learning : On receiving a query, the transit nodes “learn” the path to the source and enter the route in the forwarding table The query packet is dropped if it encounters a node which already has a route to the destination

AODV (cont’d) A link failure will trigger a query-response procedure in order to find a new route

DSR Source routing : A source indicates in a data packet’s header the sequence of intermediate nodes on the routing path DSR also takes advantage of existing route information at immediate nodes to save route search overhead

Comparisons of Flat Routing Protocol

Main topics: 1.Flat routing protocols 2.Hierarchical routing protocols 3.Geographic position assisted routing protocols

Hierarchical Routing Protocols When the network size increases, the “flat” routing schemes become infeasible Hierarchical routing is based on “organizing nodes in groups and assigning nodes different functionalities inside and outside a group”

Hierarchical Routing Protocols 1.CGSR (Clusterhead-Gateway Switch Routing) 2.HSR (Hierarchical State Routing) 3.ZRP (Zone Routing Protocol) 4.LANMAR (Landmark Ad Hoc Routing Protocol)

CGSR Partition the whole network into clusters A clusterhead is elected in each cluster A node belonging to two clusters is a called a gateway

CGSR (cont’d)

It uses the distance vector routing algorithm At each node two tables are maintained: a cluster member table and a DV routing table The cluster member table records the clusterhead for each node and is broadcast periodically

CGSR (cont’d) The routing table only maintains one entry for each cluster recording the path to its cluster head. CGSR can significantly reduce the routing table size compared to DV protocols

HSR It is a multilevel clustering-based LS routing protocol Same as CGSR, there are three kinds of nodes: clusterheads, gateways, and internal nodes As it is multilevel, new cluster heads are elected at each level and become members of the higher-level cluster

HSR HSR uses hierarchical addresses Think of identifying a soldier in the army:

ZRP A hybrid routing protocol that combines both proactive and on-demand routing strategies Each node has a predefined zone Inside zones: proactive routing Outside zones: on-demand routing ZRP provides more flexibility

LANMAR Similar to ZRP, the whole network is partitioned into groups Each group has a predetermined landmark which keeps track of the group It is very suitable for the situation that nodes are likely to move in groups

Coomparisons of Hierachical Routing Protocols

Main topics: 1.Flat routing protocols 2.Hierarchical routing protocols 3.Geographic position assisted routing protocols

Geographic Position Information Assisted Routing 1.LAR (Location-Aided Routing) 2.DREAM (Distance Routing Effect Algorithm for Mobility) 3.GPSR (Greedy Perimeter Stateless Routing)

GeoCast It uses specific geographic information to specify the destination, rather than logical node address A special computer host is in charge of receiving and sending geographic messages (GeoHost) GeoHost is responsible for forwarding the packets to local GeoRouter

LAR LAR utilizes location information to limit the area for discovering a new route to a smaller requested zone The operation is similar to DSR : LAR performs the route discovery through limited flooding

LAR (cont’d) Determine the requested zone Scheme1: estimating a circular area in which the destination is expected to be found During the route request flood, only nodes inside the request zone forward the request message

LAR (cont’d) Scheme 2 : Calculating the distance to the destination The distance is included in a route request message A node relays a request message only if its distance to the destination is less than or equal to the distance included in the request message The distance field is updated before relaying the request

DREAM It is a proactive routing protocol using location information It minimizes the routing overhead by using two principles

DREAM (cont’d) Two Principles (1) distance effect : the greater the distance separating two nodes, the slower they appear to be moving w.r.t each other (2) mobility rate : the faster a node moves, the more frequently it needs to advertise its new location

DREAM (cont’d) Each node maintains a location table, which records locations of all the nodes More frequently are the control packets sent to closer nodes The frequency of sending the control packets is adjusted based on its moving speed

GPSR It is a routing protocol that uses only neighbor location information in forwarding data packets It uses two data forwarding schemes : greedy forwarding and perimeter forwarding

Questions?

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